Sheet convey apparatus

ABSTRACT

A sheet convey apparatus includes first and second conveyor belts, an air pipe, and a rotary body. The first conveyor belt conveys a plurality of sheets. The second conveyor belt is provided downstream of the first conveyor belt in a sheet convey direction and has a convey speed lower than that of the first conveyor belt. The air pipe is provided above the first conveyor belt and discharges air obliquely downward toward a downstream side of the sheet convey direction to float a trailing edge portion of a sheet. The rotary body is rotatably supported above the first conveyor belt and guides the trailing edge portion of the sheet which has floated with the air from the air pipe.

BACKGROUND OF THE INVENTION

The present invention relates to a sheet convey apparatus which, when conveying sheets obtained by sequentially cutting a web which is fed out, conveys the sheets by lapping the leading edge and trailing edge of two successive sheets.

As a conventional sheet convey apparatus which conveys sheets by lapping the leading edge and trailing edge of two successive sheets, one as shown in U.S. Pat. No. 4,302,001 is proposed. This apparatus comprises a cutting device which cuts a paper web, the first feeding device which feeds a cut sheet, the second feeding device which is located downstream of the first feeding device in a sheet convey direction and has a sheet feed speed lower than that of the first feeding device, and a chucking means for chucking the sheets upward between the first and second feeding devices within a range where the edges of the sheet are lapped like fish scales.

According to another conventional sheet convey apparatus, one as shown in U.S. Pat. No. 5,275,394 is proposed. This apparatus comprises a belt device which conveys a sheet obtained by cutting a paper web by a cutting device, a lifting means for lifting upward the trailing edge portion of a downstream sheet which is being conveyed by the belt device, and a pickup means for chucking the lifted trailing edge portion. The leading edge portion of an upstream sheet is inserted under the trailing edge portion of the sheet chucked by the pickup means to lap the edges of the two sheets.

According to the former sheet convey apparatus described above, the sheets are conveyed with the trailing edge portion of the preceding downstream sheet being chucked by the chucking means. Thus, the sheet is rubbed by the chucking means and accordingly damaged.

According to the latter sheet convey apparatus, if the rigidity (hardness) of the sheet to be lifted by the lifting means is relatively low, sometimes the trailing edge portion of the sheet cannot be lifted to a predetermined height. In this case, the trailing edge portion of the sheet cannot be chucked by the pickup means, so the edges of the two sheets cannot be reliably lapped. Also, adjusting operation is required to adjust the lifting amount of the lifting means to match the stiffness (hardness) of the sheet.

These problems may be solved by a method of blowing discharge air to the sheet from below so that the trailing edge portion of the downstream sheet is chucked by the chucking means reliably. In this case, to reliably lap the sheets, the operation of adjusting the chucking air discharge timing is necessary so that only the trailing edge of the downstream sheet may be blown up with the discharge air but the leading edge of the upstream sheet may not be blown up. This adjusting operation is cumbersome and time-consuming because the air discharge on/off timing must be adjusted in accordance with the sheet convey speed.

The same problem arises when conveying precut sheets in a lapped state.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a sheet convey apparatus that can reliably lap the edges of sheets without damaging the sheets.

It is another object of the present invention to provide a sheet convey apparatus that does not require adjusting operation.

According to the present invention, there is provided a sheet convey apparatus comprising first convey means for conveying a plurality of sheets, second convey means provided downstream of the first convey means in a sheet convey direction and having a convey speed lower than that of the first convey means, air discharge means, provided above the first convey means, for discharging air obliquely downward toward a downstream side of the sheet convey direction to float a trailing edge portion of a sheet, and a rotary body which is rotatably supported above the first convey means and guides the trailing edge portion of the sheet which has floated with the air from the air discharge means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a sheet-fed offset rotary printing press to which a sheet convey apparatus according to the first embodiment of the present invention is applied;

FIG. 2 is a plan view of the sheet convey apparatus shown in FIG. 1;

FIG. 3 is a side view of the sheet convey apparatus shown in FIG. 1;

FIG. 4 is a partially cutaway plan view of the air flow rate adjusting device shown in FIG. 2; and

FIG. 5 is a plan view of a sheet convey apparatus according to the second embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A case will be described with reference to FIGS. 1 to 4 wherein a sheet convey apparatus according to the first embodiment of the present invention is applied to a sheet-fed offset rotary printing press.

As shown in FIG. 1, a sheet convey apparatus 1 according to this embodiment includes a roll 3 around which a web 2 is wound, a cutting device 4 which feeds separately from each other a plurality of sheets obtained by cutting the web 2 fed out from the roll 3 into a predetermined size, and a lapping unit 5 which inserts the leading edge portion of, among two sheets fed from the cutting device 4, the following sheet under the trailing edge portion of the preceding sheet and conveys the two sheets with their edges being lapped. Note that“the trailing edge portion of the preceding sheet” means“the upstream edge in the sheet convey direction of a sheet located downstream in the sheet convey direction”. Also, “the leading edge portion of the following sheet” means“the downstream edge in the sheet convey direction of a sheet located upstream in the sheet convey direction”.

A known sheet-fed offset rotary printing press 6 includes a feeder board 8 which feeds one by one the sheets conveyed from the sheet convey apparatus 1 described above, a printing unit 9 which prints the sheets fed from the feeder board 8, and a delivery unit 10 which delivers the sheets printed by the printing unit 9. The printing unit 9 includes two printing units 9A and 9B sequentially disposed in the sheet convey direction. Each of the printing units 9A and 9B includes a plate cylinder 11 to which ink and water are supplied from an inking device and dampening device (not shown), a blanket cylinder 12 which is in contact with the plate cylinder 11, and an impression cylinder 13 which opposes the blanket cylinder 12. A transfer cylinder 14 is arranged between the impression cylinders 13 of the printing units 9A and 9B.

The delivery unit 10 includes a sprocket 15 coaxial with a delivery cylinder (not shown) which opposes the impression cylinder 13 of the printing unit 9B, a sprocket 16 rotatably supported at the rear end side of the delivery unit 10, and a delivery chain 17 applied between the sprockets 15 and 16. In this arrangement, a sheet fed from the feeder board 8 is printed on its obverse surface with the first color by the printing unit 9A. The sheet is then conveyed to the printing unit 9B by the transfer cylinder 14, and its obverse surface is printed with the second color. The printed sheet is gripping-changed to the delivery pawls (not shown) of the delivery chain 17 and conveyed as the delivery chain 17 runs. When the sheet is conveyed to the rear end side of the delivery unit 10, the delivery pawls release the sheet, so that the sheet drops onto a pile board (not shown) and is stacked there.

The lapping unit 5 of the sheet convey apparatus 1 will be described with reference to FIGS. 2 and 3. The lapping unit 5 includes a first conveyor belt 20 (first convey means) which conveys a sheet 19 cut by the cutting device 4, and a second conveyor belt 21 (second convey means) which is arranged downstream (direction of an arrow A) of the first conveyor belt 20 in the sheet convey direction. The first and second conveyor belts 20 and 21 are arranged on one plane.

As shown in FIG. 2, the first conveyor belt 20 is formed of one endless belt having a width larger than the width (the length in a direction perpendicular to the sheet convey direction) of the sheet 19. The endless belt which forms the first conveyor belt 20 is looped between a first driving roller 22 and a driven roller (not shown) arranged in the vicinity of the cutting device 4 to extend in the directions of the arrow A and an arrow B. When the first driving roller 22 is driven to rotate by a first motor 23, the first conveyor belt 20 travels at a speed V1 in the direction of the arrow A.

As shown in FIG. 2, the second conveyor belt 21 is formed of one endless belt having the same width as that of the first conveyor belt 20. The endless belt which forms the second conveyor belt 21 is looped between a second driving roller 24 and a driven roller (not shown) arranged in the vicinity of the feeder board 8 to extend in the directions of the arrows A and B. When the second driving roller 24 is driven to rotate by a second motor 25, the second conveyor belt 21 travels at a speed V2 lower than the traveling speed V1 of the first conveyor belt 20 in the direction of the arrow A.

Above the first conveyor belt 20, an air pipe 26 is arranged upstream (the direction of the arrow B) of a rotary body 30 (to be described later) in the sheet convey direction. The air pipe 26 extends in the widthwise direction of the sheet 19, i.e., the first conveyor belt 20, and is connected to an air supply source (not shown) such as a compressor through a pipe 27A. The air pipe 26 has air nozzles 28 (air discharge means) that line up equidistantly on one straight line in the axial direction. As shown in FIG. 3, the air nozzles 28 are arranged such that their distal ends are directed obliquely downward toward the downstream side of the sheet convey direction (the direction of the arrow A). Air 29 discharged from the air nozzles 28 is blown to a portion between the first driving belt 20 and the rotary body 30. The air pipe 26 is pivotally supported by a pair of frames 31 (FIG. 2) which oppose each other at a predetermined gap. A blowing angle a of the air 29 discharged from the air nozzles 28 is adjusted by a stepping motor 32 (FIG. 2). The discharge speed of the air 29 is adjusted by an air flow rate adjusting device 34 (to be described later).

A gear 32 a axially mounted on the output shaft of the stepping motor 32 meshes with gears 26 a and 33 a, as shown in FIG. 2. The gear 26a is axially mounted on an end shaft 26 b of the air pipe 26. The gear 33 a is axially mounted on the rotating shaft of an encoder 33. In this arrangement, when the stepping motor 32 is driven, the air pipe 26 pivots through the gears 32 a and 26 a. The pivot amount of the air pipe 26 is detected by the encoder 33 through the gears 32 a and 33 a. When the blowing angle α of the air 29 reaches a predetermined value, the stepping motor 32 stops driving to fix the blowing angle α of the air 29.

As shown in FIG. 4, the air flow rate adjusting device 34 includes an electromagnetic valve 35 having an actuator 35 a which can advance/retreat, and a valve 36 having one end pivotally mounted on the actuator 35 a and the other end biased by a coil spring 37 in a direction to separate from the actuator 35 a. When driven by the electromagnetic valve 35, the valve 36 moves across the boundary portion of the pipe 27A and a hose 27B in a direction perpendicular to an air channel to open/close the sectional area of the air channel. The valve 36 has an air passage 36 a through which the pipe 27A communicates with the hose 27B, and an exhaust passage 36 b through which the pipe 27A communicates with outer air. In this arrangement, when the electromagnetic valve 35 is driven to change the advancing/retreating amount of the actuator 35 a, the opening amount between the pipe 27A and hose 27B is adjusted to adjust the discharge speed of the air 29 to be discharged from the air nozzles 28.

Above the first driving belt 20, as shown in FIG. 3, the rotary body 30 is arranged upstream of the first driving roller 22 in the sheet convey direction to be parallel to the first driving roller 22. The rotary body 30 is rotatably supported by the pair of frames 31 so as to extend in the widthwise direction of the sheet 19 under conveyance. The rotary body 30 is arranged to correspond to the position of a trailing edge portion 19 a of a sheet 19A when a leading edge portion 19 b of the sheet 19A conveyed by the first conveyor belt 20 separates from the first conveyor belt 20 and starts to come into contact with the second conveyor belt 21. In this arrangement, the trailing edge portion 19 a of the sheet 19A which floats with the air 29 discharged from the air nozzles 28 comes into contact with the rotary body 30, so that the floating sheet 19A is guided.

The sheet convey operation of the sheet convey apparatus with the above arrangement will be described. Air has been supplied to the air pipe 26 in advance from an air supply source (not shown) through the pipe 27A and hose 27B, and the air nozzles 28 constantly discharge the air 29. In this state, in FIG. 1, the web 2 fed out from the roll 3 is cut by the cutting device 4 into sheets each having a predetermined size. The cut sheets are sequentially fed onto the first conveyor belt 20 of the lapping unit 5. The fed sheet 19A is conveyed by the first conveyor belt 20 at the convey speed V1 in the direction of the arrow A.

When the leading edge portion 19 b of the sheet 19A separates from the first conveyor belt 20 and comes into contact with the second conveyor belt 21, as the traveling speed V2 of the second conveyor belt 21 is lower than the traveling speed V1 of the first conveyor belt 20, the convey speed of the sheet 19A also decreases. At this time, the trailing edge portion 19 a of the sheet 19A is located under the rotary body 30. The air nozzles 28 arranged upstream of the rotary body 30 in the sheet convey direction discharge the air 29 obliquely downward toward the downstream side of the sheet convey direction (direction of the arrow A).

Therefore, the air 29 enters under the trailing edge portion 19 a of the preceding sheet 19A to float the trailing edge portion 19 a. Thus, a leading edge portion 19 b of a following sheet 19B which has been conveyed by the first conveyor belt 20 at the speed V1 higher than the speed V2 is inserted under the trailing edge portion 19 a of the preceding sheet 19A. The air 29 from the air nozzles 28 urges the leading edge portion 19 b of the upstream sheet 19B against the first conveyor belt 20. Thus, the leading edge portion 19 b of the sheet 19B is reliably inserted under the trailing edge portion 19 a of the preceding sheet 19A.

The air nozzles 28 are arranged, above the first conveyor belt 20, upstream of the rotary body 30 in the sheet convey direction. Hence, even if the air 29 is constantly discharged, the upper surface of the sheet 19 on the first conveyor belt 20 is blown with air. This urges the sheet 19 against the first conveyor belt 20 so the sheet convey operation is not influenced. After that, when the sheet 19 moves to the second conveyor belt 21 and its trailing edge portion 19 a is positioned below the rotary body 30, the air 29 is blown between the lower surface of the trailing edge portion 19 a and the first conveyor belt 20 to lift up the trailing edge portion 19 a.

More specifically, even if the air 29 is discharged constantly, when the trailing edge portion 19 a of the preceding sheet 19A is positioned below the rotary body 30, the trailing edge portion 19 a floats by the air 29. The leading edge portion 19 b of the following sheet 19B is conveyed as it is pressed (urged) with the air 29 against the first conveyor belt 20. In this manner, even if the air 29 is discharged constantly, the edges of the sheets that travel continuously can be lapped reliably. Thus, the discharge timing of the air 29 need not be adjusted.

The floating trailing edge portion 19 a of the sheet 19A comes into contact with the rotary body 30 and is conveyed in the direction of the arrow A as it is guided by the rotary body 30. In this manner, as the trailing edge portion 19 a of the preceding sheet 19A is guided by the rotary body 30, it will not flutter or waves, so that uncontrolled movement of the sheet is regulated. As the rotary body 30 is rotatably supported, it is rotated in an interlocked manner by the friction generated between the outer surface of the rotary body 30 and the trailing edge portion 19 a of the sheet 19A which is in contact with the outer surface of the conveyor belt 20. Therefore, no rubbing occurs between the sheet 19A and rotary body 30, and the trailing edge portion 19 a will not be damaged. Even when the gap between the cutting device 4 and sheet-fed offset rotary printing press 6 is large, the two, first and second conveyor belts 20 and 21 as the sheet convey means can form the sheet convey path, so that the number of components decreases and the structure is simplified.

In the state wherein the trailing edge portion 19 a of the sheet 19A is guided by the rotary body 30, when the sheet 19A is further conveyed in the direction of the arrow A by the second conveyor belt 21, the trailing edge portion 19 a of the sheet 19A separates from the rotary body 30. Then, the trailing edge portion 19 a of the sheet 19A drops onto the leading edge portion 19 b of the following sheet 19B to lap it.

In this case, depending on the weight, size, or stiffness (hardness) of the sheet, if the floating amount of the trailing edge portion 19 a of the sheet 19A is not sufficient, the discharge speed of the air 29 is adjusted by the blowing angle α of the air 29 discharged from the air nozzles 28 or by the air flow rate adjusting device 34. As a result, the quantity of air 29 to be supplied under the trailing edge portion 19 a of the preceding sheet 19A increases to complement the insufficient floating amount of the trailing edge portion 19 a . Thus, the edges of the two sheets lap reliably.

The second embodiment of the present invention will be described with reference to FIG. 5. The second embodiment is different from the first embodiment described above in that the first convey means is formed of a plurality of first conveyor belts 40 and that the second convey means is formed of a plurality of second conveyor belts 41. The first and second conveyor belts 40 and 41 are formed of narrow endless belts obtained by dividing the conveyor belts 20 and 21 of the first embodiment each into a plurality of portions in the widthwise direction of the sheet to be conveyed. The first conveyor belts 40 line up equidistantly in the widthwise direction of the sheet to be conveyed, and are looped between a first driving roller 22 and a driven roller (not shown) to extend in the directions of arrows A and B.

The second conveyor belts 41 having the same total width as that of the first conveyor belts 40 line up equidistantly in the widthwise direction of the sheet to be conveyed to correspond to the first conveyor belts 40, and are looped between a second driving roller 24 and a driven roller 42 provided in the vicinity of a feeder board 8 to extend in the directions of the arrows A and B.

A plurality of air nozzles 43 formed in an air pipe 26 correspond to every other one of the first conveyor belts 40. Air discharged from the nozzles 43 is blown to diffuse in the widthwise direction of the first conveyor belts 40.

In this arrangement, when the leading edge portion of a sheet which is being conveyed by the first conveyor belts 40 in the direction of the arrow A comes into contact of the second conveyor belts 41, the convey speed of the sheet decreases. Simultaneously, the air blown from the air nozzles 43 floats the trailing edge portion of the sheet. Thus, the leading edge portion of a following sheet which is being conveyed by the first conveyor belts 40 in the direction of the arrow A is inserted under the trailing edge portion of the preceding sheet which floats. Hence, in the same manner as in the first embodiment, the two successive sheets are conveyed in the direction of the arrow A with the leading edge portion of the upstream sheet underlapping the trailing edge portion of the downstream sheet.

While belts are used in this embodiment as a means for conveying the sheet 19, the sheet may be alternatively conveyed by a rotary roller. While the air 29 is discharged constantly from the air nozzles 28, it may be alternatively discharged intermittently. While a case has been described wherein the air flow rate adjusting device 34 is used as a means for adjusting the discharge speed of the air to be discharged from the nozzles 28, the adjusting means is not limited to this. For example, when a DC motor is used as the motor of a blower that constitutes an air supply source which supplies air to the air pipe 26, the DC power supply voltage to be supplied to the motor may be adjusted. When an AC motor is used as the blower motor, the AC power supply frequency may be adjusted. Alternatively, a regulator or relief valve may be disposed midway along the pipe 27A.

In the above embodiment, the roll-type sheet is cut by the cutting device and pre cut sheets are supplied at a predetermined interval. The present invention can also naturally be applied to a case wherein pre cut sheets are conveyed in a lapping manner. The sheet to be conveyed is not limited to a paper sheet, but can be any sheet-type object, e.g., a plastic sheet or film, which can be printed on its obverse surface.

As has been described above, according to the present invention, the leading edge portion of an upstream sheet can be reliably inserted under the trailing edge portion of a downstream sheet. Therefore, the edges of two successive sheets can be lapped reliably. While the air is constantly discharged, the edges of the two sheets can be lapped reliably. Thus, the air discharge timing need not be adjusted. As the trailing edge portion of the floating sheet is guided by the rotary body, the sheet will not be damaged.

Even when the sheets are to be conveyed at a relatively long interval, this can be coped with by two sets of belts. Thus, the number of components decreases and the structure is simplified. If the floating amount of the trailing edge portion of the sheet is not sufficient, the air speed or air blowing angle may be adjusted to increase the quantity of air to be supplied under the trailing edge portion of the sheet, so that the edges of the two sheets can be lapped reliably. 

1. A sheet convey apparatus comprising: first convey means for conveying a plurality of sheets; second convey means provided downstream of said sheet convey means in a sheet convey direction and having a convey speed lower than that of said first convey means; air discharge means, provided above said first convey means, for discharging air obliquely downward toward a downstream side of the sheet convey direction to float a trailing edge portion of a sheet; and a rotary body which is rotatably supported above said first convey means and guides the trailing edge portion of the sheet which has floated with the air from said air discharge means.
 2. An apparatus according to claim 1, wherein said first and second convey means respectively comprise first and second conveyor belts arranged on one plane, and when a leading edge portion of the sheet separates from said first conveyor belt and comes into contact with said second conveyor belts, the trailing edge portion of the sheet floats by air.
 3. An apparatus according to claim 2, wherein said air discharge means constantly discharges air, while a sheet is conveyed by said first conveyor belt, the sheet is pressed against said first conveyor belt with the air blown to an upper surface thereof, and when a convey operation of a sheet is switched from said first conveyor belt to said second conveyor belt, the trailing edge portion of the sheet is lifted by the air blown between a lower surface of the trailing edge portion of the sheet and said first conveyor belt.
 4. An apparatus according to claim 2, wherein said rotary body is provided at a position to correspond to the trailing edge portion of the sheet the leading edge portion of which has separated from said first conveyor belt and has come into contact with said second conveyor belt.
 5. An apparatus according to claim 2, wherein each of said first and second conveyor belts comprises a plurality of narrow belts divided in a widthwise direction of the sheet.
 6. An apparatus according to claim 5, wherein said air discharge means comprises a plurality of nozzles which are attached to correspond to every other one of said narrow belts of said first conveyor belt.
 7. An apparatus according to claim 1, further comprising air flow rate adjusting means for adjusting a flow rate of the air to be discharged from said air discharge means.
 8. An apparatus according to claim 7, wherein said air flow rate adjusting means has a valve member which adjusts a sectional area of an air channel to change a discharge speed of the air.
 9. An apparatus according to claim 1, wherein said air discharge means comprises an air pipe which is axially, pivotally supported and to which air from an air supply source is supplied, and a nozzle which is attached to said air pipe to discharge the air supplied to said air pipe, and a discharge direction of the air from said nozzle is adjusted by pivot adjustment of said air pipe.
 10. An apparatus according to claim 1, further comprising a cutting device which sequentially cuts a leading edge of a web that is fed out and supplies a cut sheet to said first convey means.
 11. An apparatus according to claim 1, wherein said first convey means conveys the plurality of sheets to be separate from each other. 